Class f electrical tape

ABSTRACT

Disclosed herein are solvent-resistant Class F electrical tapes which comprise a backing member coated with a pressure-sensitive adhesive composition which is the polymeric product of butyl acrylate and a hydroxy-bearing monomer which is cured with a curing system comprising a metal alkoxide and an organic peroxide.

United States Patent 1 1 3,632,413

[72] Inventors Robert B. Blance 56] References u Em Lmgmeadw; UNITEDSTATES PATENTS Game" 3,269,994 8/1966 116m et al 1 17/122 x m] A I N 21%3,307,690 3/1967 Bond etal 117/122 x pp o. 1221 F1166 Apr. 2, 1969 OTHERREFERENCES 45 P d J 4, 1972 Takahashi et al., Chemical Abstracts, 88l52p, Vol. 68, [73] Assignee Monsanto Company 6 St L i M Temm et al.,Chemical Abstracts, 33288 m, Vol. 67, 1967.

Primary ExaminerWilliam D. Martin Assistant ExaminerBemard D. Pianalto[54] CLASS F ELECTRICAL TAPE Attorneys-William J. Farrington, Arthur E.Hoffman and 10 Claims No Drawings Russell H. Schlattrnan 1521 u.s.c1 1171221 117/161 UC, 260/8l.6 51 1m.c1 c093 7/02 ABSTRACT: Disclosed r in arl nt-r sistant Class F 117/122 p electrical tapes which comprise abacking member coated 122 PA, 122 pp 1 gem/ 1 with a pressure-sensitiveadhesive composition which is the polymeric product of butyl acrylateand a hydroxy-bearing monomer which is cured with a curing systemcomprising a metal alkoxide and an organic peroxide.

[50] Field of Search.

CLASS F ELECTRICAL TAPE BACKGROUND OF THE INVENTION 1. Field of theInvention This invention is directed to electrical tapes. Morespecifically, this application is directed to solvent resistantelectrical tapes which comprises an inert backing member coated with apressure-sensitive adhesive composition which can be used in Class Felectrical applications as both an insulating and bonding member.

2. Description of the Prior Art Pressure-sensitive electrical tapes arewell known in the prior art. These tapes are used as insulatingmaterials and for the purpose of bonding components in electricalsystems. The tapes of the prior art are based on pressure-sensitiveadhesive compositions such as carboxylic acid containing copolymers andcopolymers of vinyl acetate and esters of acrylic or methacrylic acid.However, a major deficiency of these polymers is their inability towithstand the prolonged exposure to high temperatures which is requiredfor use in Class F electrical systems. A Class F electrical system isdefined as one which can withstand 20,000 hours at 155 C. under a one(1) kilovolt (kv.) load.

All of the components of a Class F system, the electrical hardware aswell as the backing member and adhesive component of the tape, must beable to withstand the specified exposure. Moreover, any tape intendedfor use in Class F electrical insulation must be free of materials whichwould cause corrosion of the conductive parts.

Carboxylic acid-containing polymers are a potential source of corrosionto the copper components of electrical systems. Other polymers whichgenerate even small amounts of free volatile acid upon heating, such asvinyl acetate containing polymers which generate acetic acid, are alsopotential sources of corrosion. This corrosion causes voltage breakdownor current leakage thereby shortening the useful life of the electricalsystems.

In addition to lacking the necessary thermal stability and freedom fromcorrosion causing constituents many of the polymers of the prior artlack the necessary oil and solvent resistance which is required in thoseapplications where the electrical system is exposed to oil and/ororganic solvents such as in hermetic-type units and where the electricalsystem is coated with organic solvent-based insulating varnish sealants.

Although those polymers which are prepared by polymerizing an acrylicacid ester with a carboxylic acid monomer and/or vinyl acetate arewell-known in the art of their pressure-sensitive adhesive properties,these materials are generally regarded as unsuitable as an adhesivecomponent in Class F electrical tapes because of the deficienciespointed out above. Consequently, those skilled in the art must resort tothe more costly silicon based pressure-sensitive adhesives for Class Fapplication. Thus, there exists in the art a definite need for oil andsolvent resistant acrylic based Class F electrical tape which is freefrom components which would cause corrosion of the conductive parts ofthe electrical system while withstanding prolonged exposure to hightemperatures which is required for a Class F rating.

SUMMARY OF THE INVENTION The present invention solves the aforementionedproblems by providing thermally stable, oil and solvent-resistantacrylic based Class F electrical tapes which minimize the danger ofcorrosion in electrical systems.

The Class F electrical tapes of the present invention comprise athermally stable backing member which is coated with a pressuresensitive adhesive composition which is the interpolymerization productof from 80 to 98 weight percent of butyl acrylate and from 2 to 20weight percent of a hydroxybearing monomer selected from the groupconsisting of hydroxy alkyl acrylates, hydroxy alkyl methacrylates, 2-hydroxy alkyl vinyl ether, hydroxy alkyl fumarates and hydroxy alkylmaleates wherein the alkyl group contains from two to four carbon atoms.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The backing members which areused in the present invention must also be able to meet Class Frequirements. Consequently, the choice of a backing member is limited tothose materials which are oil and solvent resistant and which canwithstand prolonged exposure to high temperatures. Moreover, the backingmember must be an electrical insulator which is free of components whichcould cause corrosion to the conductive parts of the system. Examples ofsuitable backing members include sheets, films and cloths prepared frompolyethylene terephthalate, mica paper, glass, polytetrafluoroethylene,polytrifluoromonochloroethylene, polyimides, etc.

The interpolymers of this invention are conveniently prepared by organicsolvent polymerization techniques involving in some cases delayedaddition of monomer. The time interval for the delayed addition mayrange from about 10 to about 600 minutes and longer. The techniques ingeneral, involve the polymerization of the respective monomer mixturesin suitable organic solvents, the polymerization being initiated byheat-activated free radical initiators.

The choice of solvents for the interpolymer used in the practice of thisinvention is governed by the solubility require ments of the monomersand the resulting interpolymers in that both the monomers and theresulting interpolymers should be soluble in the selected solvent ormixtures of solvents. A further requirement is that the interpolymersolution should contain less than 2 percent water by weight, based onthe total weight of the solvent, in order to avoid adverse interferencewith any metal alkoxide component which may be used to cross-link thepolymer as is discussed below. More preferably, the interpolymersolution should contain less than 1 percent water by weight.

Examples of suitable solvents for the interpolymers include aromaticsolvents such as benzene, toluene, xylene, etc. Suitable aliphaticsolvents include alcohols such as methanol, ethanol, propanol, butanol,etc.; esters such asethyl acetate, propyl acetate, isopropyl acetate,butyl acetate, etc.; ketones such as methyl ethyl ketone, acetone, etc.;aliphatic hydrocarbons such as pentane, hexane, etc. Especially usefulare mixtures of the foregoing.

Polymerization initiators suitable for the preparation of the specialinterpolymers of this invention include free radical azo-type initiatorssuch as: a, a'-azodiisobutyronitrile; 2-(tbutylazo)isobutyronitrile;2-t-butylazo-2-phenylpropane; l-tbutylazo-;-phenylcyclohexane; l-cyano-1 t-butylazo cyclohexane; etc.

Other polymerization initiators would include organic peroxides which donot yield monomeric acid products capable of corroding copper wire.Examples of these would include: t-butylhydroperoxide; t-butyl peroxide;1, l-bis(tbutylperoxy )3 ,3 ,S-trimethylcyclohexane; 2,2-bis(t-butylperoxy)butane; 2-methoxy-2-t-butylperoxypropane;2,4,6-tri(t-butylperoxy)triazine; t-amyl peroxide; cumyl peroxide; etc.Ultraviolet light and gamma radiation can also be used to initiate thepolymerization reaction.

The interpolymers of the present invention are cured to provide furtherthermal stability, to improve their solvent resistance to transformeroil and impregnating varnish, to increase their load holding power, andto enhance the permanence of the bond. Curing may be effected with metalalkoxides, peroxides or blocked isocyanates. These curing agents can beincorporated in the resin solution without adverse effect on thesolution stability.

Metallic alkoxides such as titanium butoxide, when they are formulatedwith the resin in alcohol solution, offer the advantage of rapid cure byformation of polyalkoxides when the solution is dried. Thus, initialload-holding ability is readily obtained so that the tape can withstandthe initial exposure to baking which is required to expel moisture fromthe assembly without softening excessively and yielding to shear forces.

Metal alkoxides which are used in the present invention are thoserepresented by the following general formula:

where M is a metal selected from the group consisting of Groups ll toVlll of the periodic table; R is selected from the group consisting ofalkyl radicals of from one to eight carbon atoms and aryl radicals offrom six to l6 carbon atoms. R is selected from the group consisting ofaliphatic and substituted aliphatic radicals containing from one to 18carbon atoms; in is an integer whose value is zero or greater and n isan integer of at least 2, wherein the sum of m+n is greater than one (l)and is equal to the valance of the metal represented by M.

Examples of metal alkoxides for use in the practice of this inventioninclude the following: magnesium ethoxide, calcium ethoxide, strontiumethoxide, barium ethoxide, aluminum ethoxide, aluminum isopropoxide,lanthanum t-butoxide, ferric ethoxide, ferric isopropoxide, titaniumethoxide, titanium isopropoxide, titanium butoxide, zirconium ethoxide,zirconium isopropoxide, zirconium butoxide. hafnium ethoxide, hafniumisopropoxide, cerium isopropoxide, germanium isopropoxide, stannicethoxide, stannic isopropoxide, vanadium isopropoxide, chromiumt-butoxide, niobium ethoxide, niobium isopropoxide, potassium zirconiumethoxide, magnesium aluminum ethoxide, potassium aluminum butoxide,sodium stannic ethoxide, and alkyl metal alkoxides such as diethoxyethyl aluminum, dibutoxy diphenyl titanium, phenyl triisopropoxytitanium, dimethyl diisopropoxy titanium, dibutyl dimethoxy tin.Especially preferred are liquid alkoxides such as titanium isopropoxideand titanium butoxide.

The manner in which the metal alkoxide is added to the polymer solutionis very critical and precautions must be taken in order to prevent thegelation of the resin solution. The metal alkoxide should be dissolvedin a suitable solvent prior to adding the metal alkoxide to the polymersolution. Suitable solvents for the metal alkoxide include alcohols andcarboxylic acids, preferably the lower boiling alcohols such asaliphatic alcohols containing from one to four carbon atoms, e.g.,methanol, ethanol, propanol, and butanol, and lower boiling aliphaticacids containing from two to four carbon atoms, e.g., acetic, propionicand butyric acids. In the event that an acid solvent is used,precautions must be taken to remove all of the solvent from the resinduring the drying stage in order to avoid having corrosive components inthe electrical tape. Especially preferred are the alcoholic solvents.The solvent used to dissolve the metal alkoxide should be substantiallyanhydrous, i.e., contain less than 1 percent water by weight and morepreferably less than 0.5 percent water by weight.

The amount of metal alkoxide used in a given polymer system will dependupon the nature of the system and the degree of cure desired. Ingeneral, at least 0.01 equivalent of metal alkoxide per equivalent ofactive hydrogen in the resin should be used. Preferably, one would use0.05 equivalent of metal alkoxide and more preferably 0.l equivalent ofmetal alkoxide, per equivalent of active hydrogen in the resin. Themaximum amount of metal alkoxide used will depend on the particularresin system and metal alkoxide used and the degree of cross linkingdesired in the system. From a practical standpoint, no significantimprovement in resin properties is found when using metal alkoxide inexcess of five (5.0) equivalents per equivalent of active hydrogen inthe polymer. The reference to active hydrogen in the resin in regard tothe amount of metal alkoxide to be used is to the hydrogen on thehydroxyl groups of the hydroxy-bearing monomers.

Peroxides such as t-butyl peroxide and cumyl peroxide may be utilized ina heat-activated cure. These peroxides are chosen because they arehighly efficient cross-linking agents which do not yield acid productsupon decomposition so that no corrosion of the metal components in theelectrical system can occur. A high degree of cure can be obtained withthese peroxides at elevated temperatures. Other suitable peroxides foruse as a curing agent include those listed above as polymerizationinitiators.

The amount of peroxide curing agent used in the practice of thisinvention is in the range of from 0.1 percent to 3.0 percent by weightbased on the weight of solid polymer.

Blocked isocyanates such as the phenol adduct of tolylene diisocyanatemay also yield a heat activated cure by interaction with hydroxyl toproduce a high cross-link density, dependent on the amount of hydroxymonomer introduced into the acrylate resin. Phenol is liberated duringcure and may improve the thermal stability by functioning as anantioxidant.

While each of the methods of cure may be utilized alone, a combinationof the alkoxide and peroxide cures is preferred. In this manner, a driedcoated backing member is obtained, which is pressure sensitive but crosslinked to a sufficient degree by the alkoxide to acquire excellentinitial load-holding ability. This coated substrate cures further viathe peroxide curing mechanism to a densely cross-linked network at thebaking temperature of equipment (180 to 300 F. for 30 minutes to 18hours) so that the final resin has excellent oil and solvent resistanceas well as excellent holding ability.

The following examples are set forth in illustration of the presentinvention and are not to be construed as limitations thereof. All partsand percentages are by weight unless otherwise specified and theexpressions polymer," copolymer" and interpolymer are usedinterchangeably.

EXAMPLE 1 This example illustrates the superior pressure-sensitiveadhesive compositions of the present invention. Ninety-five parts ofbutyl acrylate, and 5 parts of 2-hydroxy ethyl methacrylate areinterpolymerized in a L5 to l ethyl acetate/anhydrous ethanol solventpair. One-third of the monomeric charge is added initially to thereaction vessel and the remaining two-thirds of the monomeric charge isdelayed into the vessel over a minute period.

The resulting polymer solution has a solids content of 37 percent and aBrookfield solution viscosity of 7,500 centipoises at 25 C.

The following examples 2 to 12 are set forth to illustrate therelatively poor thermal stability that is obtained with thepressure-sensitive copolymers of the prior art. These polymers aretested for thermal stability using thermogravimetric analytical methods.The results of the thermogravimetric analyses are listed in table 1below.

EXAMPLE 2 This example illustrates a commercial pressure sensitiveadhesive for electrical tapes.

EXAMPLE 3 Fifty (50) parts of vinyl acetate and 50 parts of Z-ethylhexyl acrylate are polymerized in a l/2/1 hexane/toluene/ethyl acetatesolvent system. The resulting polymeric solution has a solids content of40 percent and a Brookfield viscosity of about 800 centipoises.

EXAMPLE 4 An interpolymer is prepared from 45 parts of vinyl acetate, 50parts of Z-ethyl hexyl acrylate and 5 parts of hydroxy ethylmethacrylatein the solvent system of example 1. The resulting polymer has a solidscontent of 31 percent and a Brookfield viscosity of 600 centipoises.

EXAMPLE 5 The polymeric solution prepared in example 3 above isformulated with 0.4 percent titanium butoxide according to the procedureoutlined in example 8 below.

EXAMPLE 6 has a solids content of about 40 percent and a Brookfieldsolution viscosity of 10,000 centipoises.

The polymers prepared in examples I to 6 above are subjected tothermogravimetric analysis (TGA) in a nitrogen atmosphere using a DuPont 950 Thermogravimetric Analyzer. The polymers are scanned over therange of from 25 C. to 450 C. at a heating rate of 5 C. per minute. Thepercent weight loss for the polymers at 350 C. during the TGA scan isreported in table 1 below.

TABLE I PERCENT WEIGHT LOSS AT 350 C. UNDER NITROGEN ATMOSPHERE ExampleWeight Loss OVIhLHN- The thermogravimetric analysis data shown in table1 is an index to the suitability of these materials for use as thepressure-sensitive adhesive component in Class F systems. The preferredClass F adhesives are those which exhibit a weight loss at 350 C. undera nitrogen atmosphere of less than percent and more preferably less than7.5 percent.

The date in table 1 illustrate the superior thermal properties which areexhibited by the polymeric compositions of the present invention. Thepolymer of example 1, which represents one of the preferred compositionsof the present invention, exhibits only 5 percent weight loss at 350 C.The superior thermal stability of this material makes it especiallysuitable as the adhesive component for Class F electrical tapes. Thissuitability for Class F applications is unexpected because copolymers ofbutyl acrylate are notoriously soft and thermoplastic. Consequently,these materials were generally regarded as being unsuitable for thoseapplications requiring prolonged exposure to elevated temperatures.

The polymer of example 2, which is a commercially available pressuresensitive electrical tape composition exhibits 1.6 times as much weightloss as does the polymer of example 1. Furthermore, the polymer ofexample 2 contains about 5 percent carboxylic acid groups which provideloci for copper corrosion which would lead to voltage breakdown orcurrent leakage and eventually breakdown in the electrical system inwhich this interpolymer is used.

Examples 3 and 4 illustrate the poor thermal stabilities ofpressure-sensitive adhesives which contain vinyl acetate as a comonomer.In example 5 titanium butoxide is added to the polymeric composition ofexample 10. However, no increase in thermal stability is obtained. Asstated above, this thermal instability is due in part to the presence ofvinyl acetate in the polymeric composition.

Example 6 illustrates an all acrylate system wherein a combination ofacrylic acid and glycidyl acrylate is used to provide cross linking ofthe polymeric composition. However, this system does not exhibit thethermal stability of the preferred polymeric composition of example I.

The following Examples 7 and 8 illustrate the superiorpressure-sensitive characteristics of the formulated polymericcompositions of the present invention as measured by a con ventionalcreep test. In these examples the polymeric solutions are coated on apolyethylene terephthalate tape and cured for 2 minutes at 95 C., so asto give a dried polymeric film 1 mil thick. One-half-inch strips of thecoated tape are cut and applied to mild steel panels so as to give a0.25-sq.in.-bond. One (1) hour after the strips are adhered to the panelone (1) pound loads are attached to the free end of the tape and thetime to bond failure is measured.

EXAMPLE 7 In this example the copolymer used is that prepared in exampleA tape is prepared and tested for creep resistance. The adhesive bondfailed in the creep test in less than 10 minutes.

EXAMPLE 8 Example 7 is repeated here except that lOO grams of thepolymer solution is formulated with titanium butoxide. A 10 percent byweight solution of titanium butoxide in anhydrous ethanol is preparedand then added to the polymer solution prepared in example 1 usingvigorous agitation. The resulting formulation contains 0.4 percent byweight of titanium butoxide based on the weight of the polymer.

A tape is prepared and tested for creep resistance. The adhesive bond isstill intact after three months.

EXAMPLE 9 Example 8 is repeated here except that titanium isopropoxideis used in place of the titanium butoxide used in example 8. Comparableresults are obtained,

EXAMPLE 10 One hundred grams of the unformulated polymer solution(37percent solids) prepared in example 1 and 5.4 g. of Mondur S-blockedisocyanate supplied by Mobay Chemical Company are blended together. Theblend is coated on a film of polyethylene terephthalate and dried for 2minutes at 95 C. The bond fails in 10 minutes in the creep test. Afterbaking at 300 F. for 30 minutes, the adhesive bond is still intact atthe end of 3 months. The solvent resistance of this material isexcellent.

EXAMPLE 1 1 In this example a solution of 2,2-bis(t-butyl peroxy)butaneis dissolved in anhydrous ethanol. This solution is then added to thetitanium butoxide containing composition of example 8 so as to give a2,2-bis(t-butyl peroxy)butane content of 0.5 percent by weight based onthe weight of the polymeric composition. The polymer is then coated on afilm of polyethylene terephthalate so as to give a 1 mil dry film of thepolymer. The film is dried at 25 C. for 24 hours and then tested in thecreep test described above. The adhesive bond is still intact at the endof 3 months.

The polymeric solutions of examples 7, 8, 9 and l l are coated onto aglass cloth so as to give a S-mil film of the dried polymer. The filmsare then baked for 30 minutes at 180 F. in order to simulate theconditions which are normally used to remove the moisture fromelectrical assemblies. The coated strips are then immersed into xylene,Solvesso, alcohol, nmethyl pyrrolidone and cresylic acid solvents for 24hours. After this time the strips are examined and those prepared usingthe polymeric compositions of examples 8 and 9 exhibit only very slightswelling while the composition of example 1 l exhibits virtually noswelling.

This excellent resistance to solvent attach was not observed in thepolymer of example 7 which does not contain a curing agent. This sampleswelled excessively and was partially dissolved in the solvents.

EXAMPLE 12 A transformer wrapping tape is prepared by coating a glasscloth with the formulated polymeric composition of example 8 so as toobtain a dried polymeric film one (l)-mil thick. The coated glass clothis then dried in a circulating air oven for 2 minutes at 95 C. The tapeis tested for thermal stability, holding power and solvent resistanceand found to be excellent in all respects.

EXAMPLE 13 Example 12 is repeated here except that the backing member isa polyimide film which is prepared from pyromellitic dianhydride andmethylene dianiline. Comparable results are obtained.

EXAMPLE 14 Example 12 is repeated here except using the adhesivecomposition of example 11. Comparable results are obtained in thethermal stability and creep tests. Superior results are obtained in thesolvent resistance tests.

EXAMPLE 15 Example 14 is repeated here except that the backing member isa polyimide film which is prepared from pyromellitic dianhydride andmethylene dianiline. Comparable results are obtained EXAMPLE 1 6 TABLEII SUMMARY OF EXAMPLES 17 to 21 Partsbulyl- Example l-lydroxy MonomerUsed acrylate/hydroxy monomer l7 hydroxy ethyl acrylate 97/3 l8 hydroxypropyl lumarate 92/8 I) hydroxy ethyl methacrylate 90/l0 20 hydroxyethyl methacrylate 87/13 21 Z-hydroxy ethyl vinyl ether 95/5 While thepresent invention has been described with particular reference tocertain specific embodiments thereof, it will be understood that certainchanges, substitutions and modifications may be made therein withoutdeparting from the scope thereof. This invention also contemplates theuse of thermally stable noncorrosive fillers, extenders, stabilizers,tackifiers, dyes, etc., in the polymeric compositions of this invention.

What is claimed is:

l. A Class F electrical tape which is free from components which wouldcause corrosion of the conductive parts of the electrical system towhich it is applied, which tape comprises a backing member coated with apressure-sensitive adhesive composition which is the interpolymerizationproduct of from 80 to 98 weight percent of butyl acrylate and 2 to 20weight percent of a hydroxy-bearing monomer selected from the groupconsisting of hydroxy alkyl acrylates, hydroxy alkyl methacrylates,Z-hydroxy alkyl vinyl ether, hydroxy alkyl fumarates and hydroxy alkylmaleates wherein thealkyl group contains from two to four carbon atoms;wherein the adhesive composition contains a curing system whichcomprises: (a)

from 0.1 to 5.0 equivalents of metal alkoxide per equivalent of activehydrogen in the interpolymerization product; and (b) from 0.1 to 3.0percent by weight, based on the weight of the interpolymerizationproduct of an organic peroxide which does not yield acid products upondecomposition.

2. A Class F electrical tape as in claim 1 wherein thepressure-sensitive adhesive composition is the interpolymerizationproduct of butyl acrylate and hydrox ethyl metha crylate.

3. A class F electrical tape as in c arm 2 wherein the metal alkoxide isselected from the group consisting of titanium isopropoxide and titaniumbutoxide.

4. A Class F electrical tape as in claim 3 wherein the backing member isselected from the group consisting of polytetrafluoroethylene,polyethylene terephthalate, polyimide and glass.

5. A Class F electrical tape as in claim 3 wherein the organic peroxideis selected from the group consisting of t-butyl peroxide and cumylperoxide.

6. A class F electrical tape which is free from components which wouldcause corrosion of the conductive parts of the electrical system towhich it is applied, which tape comprises a backing member coated with apressure-sensitive adhesive composition which is the interpolymerizationproduct of from to 98 weight percent of butyl acrylate and 2 to 20weight percent of a hydroxybearing monomer selected from the groupconsisting of hydroxy alkyl acrylates, hydroxy alkyl methacrylates,2-hydroxy alkyl vinyl ether, hydroxy alkyl fumarates and hydroxy alkylmaleates wherein the alkyl group contains from two to four carbon atoms;wherein the adhesive composition contains a curing system whichcomprises: (a) from 0.1 to 5.0 equivalents of metal alkoxide perequivalent of active hydrogen in the interpolymerization product; and(b) from 0.1 to 3.0 percent by weight, based on the weight of theinterpolymerization product of an organic peroxide which does not yieldacid products upon decomposition selected from the group consisting oft-butylhydroperoxide; t-butyl peroxide; 1 1 -bis( t-butyl-peroxy )3 ,3,5-trimethylcyclohexane; 2,2-bis(t-butylperoxy)butane;Z-methoxy-Z-t-butylperoxypropane; 2,4,6-tri(t-butylperoxy)triazine;t-amyl peroxide; and cumyl peroxide.

7. A Class F electrical tape as in claim 6 wherein thepressure-sensitive adhesive composition is the interpolymerizationproduct of butyl acrylate and 2-hydroxyethyl methacrylate.

8. A Class F electrical tape as in claim 6 wherein the metal alkoxide isselected from the group consisting of titanium isopropoxide and titaniumbutoxide.

9. A Class F electrical tape as in claim 6 wherein the backing member isselected from the group consisting of polytetrafluoroethylene,polyethylene terephthalate, polyimide and glass.

10. A class F electrical tape which is free from components which wouldcause corrosion of the conductive parts of the electrical system towhich it is applied, which tape comprises a backing member coated with apressure-sensitive adhesive composition which is the interpolymerizationproduct of 80-98 weight percent butyl acrylate and 2-20 weight percentZ-hydroxyethyl methacrylate; wherein the adhesive composition contains acuring system which comprises: (a) from 0.1 to 5.0 equivalents perequivalents of active hydrogen in the adhesive composition of a metalalkoxide selected from the group consisting of titanium isopropoxide andtitanium butoxide; and (b) from 0.1 percent to 3.0 percent by weight ofan organic peroxide selected from the group consisting of t-butylperoxide and cumyl peroxide.

2. A Class F electrical tape as in claim 1 wherein thepressure-sensitive adhesive composition is the interpolymerizationproduct of butyl acrylate and hydroxy ethyl methacrylate.
 3. A class Felectrical tape as in claim 2 wherein the metal alkoxide is selectedfrom the group consisting of titanium isopropoxide and titaniumbutoxide.
 4. A Class F electrical tape as in claim 3 wherein the backingmember is selected from the group consisting of polytetrafluoroethylene,polyethylene terephthalate, polyimide and glass.
 5. A Class F electricaltape as in claim 3 wherein the organic peroxide is selected from thegroup consisting of t-butyl peroxide and cumyl peroxide.
 6. A class Felectrical tape which is free from components which would causecorrosion of the conductive parts of the electrical system to which itis applied, which tape comprises a backing member coated with apressure-sensitive adhesive composition which is the interpolymerizationproduct of from 80 to 98 weight percent of butyl acrylate and 2 to 20weight percent of a hydroxy-bearing monomer selected from the groupconsisting of hydroxy alkyl acrylates, hydroxy alkyl methacrylates,2-hydroxy alkyl vinyl ether, hydroxy alkyl fumarates and hydroxy alkylmaleates wherein the alkyl group contains from two to four carbon atoms;wherein the adhesive composition contains a curing system whichcomprises: (a) from 0.1 to 5.0 equivalents of metal alkoxide perequivalent of active hydrogen in the interpolymerization product; and(b) from 0.1 to 3.0 percent by weight, based on the weight of theinterpolymerization product of an organic peroxide which does not yieldacid products upon decomposition selected from the group consisting oft-butylhydroperoxide; t-butyl peroxide; 1,1-bis(t-butyl-peroxy)3,3,5-trimethylcyclohexane; 2,2-bis(t-butylperoxy)butane;2-methoxy-2-t-butylperoxy-propane; 2,4,6-tri(t-butylperoxy)triazine;t-amyl peroxide; and cumyl peroxide.
 7. A Class F electrical tape as inclaim 6 wherein the pressure-sensitive adhesive composition is theinterpolymerization product of butyl acrylate and 2-hydroxyethylmethacrylate.
 8. A Class F electrical tape as in claim 6 wherein themetal alkoxide is selected from the group consisting of titaniumisopropoxide and titanium butoxide.
 9. A Class F electrical tape as inclaim 6 wherein the backing member is selected from the group consistingof polytetrafluoroethylene, polyethylene terephthalate, polyimide andglass.
 10. A class F electrical tape which is free from components whichwould cause corrosion of the conductive parts of the electrical systemto which it is applied, which tape comprises a backing member coatedwith a pressure-sensitive adhesive composition which is theinterpolymerization product of 80- 98 weight percent butyl acrylate and2- 20 weight percent 2-hydroxyethyl methacrylate; wherein the adhesivecomposition contains a curing system which comprises: (a) from 0.1 to5.0 equivalents per equivalents of active hydrogen in the adhesivecomposition of a metal alkoxide selected from the group consisting oftitanium isopropoxide and titanium butoxide; and (b) from 0.1 percent to3.0 percent by weight of an organic peroxide selected from the groupconsisting of t-butyl peroxide and cumyl peroxide.